This invention relates to an operator-tended machine having a protective fingerguard.
Operator-tended machines are known--for example machines for securing snap fasteners, rivets and the like to workpieces--in which a fingerguard is provided which also holds down the workpiece and controls the machine drive in dependence upon its position relative to the workpiece support (Published German Application 2,556,516). The workpiece support is provided on a rigid arm of the machine; the same arm also carries the stationary lower tool of the cooperating tool set of the machine. It follows that the workpiece support cannot move relative to the lower tool.
This arrangement is satisfactory as long as the overall height of workpieces to be processed is not too substantial. Once this height exceeds a certain dimension, however, and the fingerguard is lowered from above onto the workpiece resting on the support, the processing operation by the machine may already have to start when the upper tool and fingerguard are still spaced from the workpiece support by a distance which is greater than the permissible safety distance. In such an event the fingerguard will not allow the machine to operate, since it will encounter the workpiece during descent towards the support and react to it as a danger to the operator, i.e., by preventing machine operation. This means that on a machine of the type mentioned above tall workpieces cannot be processed, unless the drive arrangement for moving the fingerguard is so modified that the permissible safety distance is related not to the surface of the workpiece support, but instead to a level located higher than this surface. Of course, this requires machine alterations, which is time-consuming; moreover, these alterations must be reversed again if the same machine is subsequently to be able to operate again on workpieces which are less tall.